In electrophotographic applications such as xerography, a charge retentive surface is electrostatically charged and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder or powder suspension referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is well known and useful for light lens copying from an original and printing applications from electronically generated or stored originals, where a charged surface may be imagewise discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operate similarly. In a slightly different arrangement, toner may be transferred to an intermediate surface, prior to retransfer to a final substrate.
Transfer of toner from the charge retentive surface to the final substrate is commonly accomplished electrostatically. A developed toner image is held on the charge retentive surface with electrostatic and mechanical forces. A substrate (such as a copy sheet) is brought into intimate contact with the surface, sandwiching the toner thereinbetween. An electrostatic transfer charging device, such as a corotron, applies a charge to the back side of the sheet, to attract the toner image to the sheet.
Unfortunately, the interface between the sheet and the charge retentive surface is not always optimal. Particularly with non-flat sheets, such as sheets that have already passed through a fixing operation such as heat and/or pressure fusing, or perforated sheets, or sheets that are brought into imperfect contact with the charge retentive surface, the contact between the sheet and the charge retentive surface may be nonuniform, characterized by gaps where contact has failed. There is a tendency for toner not to transfer across these gaps. A copy quality defect referred to as transfer deletion results.
That acoustic agitation or vibration of a surface can enhance toner release therefrom is known, as described by U.S. Pat. Nos. 4,111,546 to Maret, 4,684,242 to Schultz, 4,007,982 to Stange, 4,121,947 to Hemphill, Xerox Disclosure Journal "Floating Diaphragm Vacuum Shoe", by Hull et al., Vol. 2, No. 6, November/December 1977, U.S. Pat. Nos. 3,653,758 to Trimmer et al., 4,546,722 to Toda et al., 4,794,878 to Connors et al., 4,833,503 to Snelling, Japanese Published Patent Appl. 62-195685, U.S. Pat. No. 3,854,974 to Sato et al., and French patent No. 2,280,115.
Resonators for applying vibrational energy to some other member are known, for example in U.S. Pat. Nos. 4,363,992 to Holze, Jr., 3,113,225 to Kleesattel et al., 3,733,238 to Long et al., and 3,713,987 to Low.
Coupling of vibrational energy to a surface has been considered in Defensive Publication T893,001 by Fisler. U.S. Pat. Nos. 3,635,762 to Ott et al., 3,422,479 to Jeffee, 4,483,034 to Ensminger and 3,190,793 Starke.
In the ultrasonic welding horn art, as exemplified by U.S. Pat. No. 4,363,992 to Holze, Jr., where blade-type welding horns are used for applying high frequency energy to surfaces, it is known that the provision of slots through the horn perpendicular to the direction in which the welding horn extends, reduces undesirable mechanical coupling of effects across the contacting horn surface.
It has been noted that even with fully segmented horns, as shown in U.S. Pat. No. 5,025,291 to Nowak et al., there is a fall-off in response of the resonator at the outer edges of the device. A similar fall off is shown in U.S. Pat. No. 4,363,992 to Holze, Jr., at FIG. 2, showing the response of the resonator of FIG. 1.
All the references cited herein are specifically incorporated by reference for their teachings.